Sponge rubber padding



Aug. 1l,- 1970 J; o. PRoHAsKA- ETL 3,523,860

I l SPONGE RUBBER PADDING Filed Apr1 4. 196e s sheets-sheet 1 Aug. 11,1970 .1.0. PROHAsKA ETAL 3,523,860

SPONGE RUBBER PADDING ."5 Sheets-Sheet 2 Filed April 4. 1966 Jan 0.@aids Z Z. @ono/JM kfsopal,

7 a //9 /20 INVENTORS,

Aug. l, 1970 .1.0. PRoHAsKA ETAL 3,523,860

SPONGE RUBBER PADDING Filed April 4. 196e s speen-sheet United StatesPatent O 3,523,860 SPONGE RUBBER PADDING John 0. Prohaska and Donald M.Wysopal, Capistrano Beach, Calif., assignors to Ludlow Corporation, LosAngeles, Calif., a corporation of Massachusetts Continuation-impart ofapplication Ser. No. 431,516,

Feb. 10, 1965. This application Apr. 4, 1966, Ser.

Int. Cl. B32b 3/26, 5/18 U.S. Cl. 161-122 8 Claims ABSTRACT F THEDISCLOSURE This is a continuation-impart of patent application Ser. No.431,516 tiled Feb. l0, 1965 and issued as U.S. Pat. No. 3,426,388.

The present invention is particularly applicable to plastice yieldableresilient material for use as a carpet underlay of which sponge rubberis an example and it will be described with particular referencethereto; however, it is to he appreciated that the invention has muchbroader applications and may be equally applied to padding of yieldableresilient material used for other purposes.

Carpet underlay has long taken the form of a flat sheet of blo-wn spongenatural or synthetic rubber having a fabric backing adhered theretowhich is produced by laying a sheet of unblown rubber onto a tiatconveyor and pressing a coarse mesh fabric into the top of the rubbersheet either before or during the blowing and curing operation thereof.

More recently, such underlay has been produced by laying a sheet ofunblown sponge rubber upon an open grid-like member, such as an openmesh conveyor belt, having spaced narrow supporting surfaces andopenings therebetween so that the sponge rubber sags naturally into theopenings to form a plurality of spaced downwardly extending and roundedprotrusions or buttons. The rubber thus has a watlied or corrugatedconstruction. As the rubber sags, an open meshed fabric is laid on Itherubber so as to extend across the valleys of the corrugations and reston the peaks thereof. This fabric adheres to these peaks as before, bybeing pressed into the sponge rubber, either before or during theblowing and curing thereof and becomes a backing for the underlay givingit lateral strength.

More recently, and as described in patent application Ser. No. 291,494,tiled June 28, 1963, the open mesh fabric backing sheet has been madegas impervious by calendering into its interstices a sheet ofnon-blowing rubber. With this arrangement, expanding gases escaping fromthe blowing sponge rubber into the valleys of the corrugations aretrapped and force the rubber downwardly .a greater distance than wouldotherwise be the case. The buttons or protrusions are hollow and definewith the backing sheet a generally closed cavity.

In either event, the outer surfacs of the protrusions or buttons aregenerally rounded (in the shape of a catenary) and substantial portionsof the surface are at a substantial angle to the vertical. Thus thebuttons are weak mechanically in this vertical direction. Also the icesurfaces of the buttons or protrusions have an unsightly texturedsurface. Moreover obtaining a uniform vertical dimension on all of theprotrusions is quite ditiicult.

A still further problem of prior processes is that only atmosphericpressure opposes the expansion of the sponge rubber resulting in aproduct having different and inferior physical properties to the samecompound cured under pressure in a hydraulic press or in a closedcavity.

A further problem, recognized by the present invention, is that thesponge rubber when curing is exposed to a hot oxygen bearing atmospheresimilar to that used in one of the most severe age resistance tests usedon rubber products. Thus, in heated platen press curing systems, air iscarried into the curing unit by the movement of the rubber. In ovencuring systems, the oxygen content of the air is somewhat reducedthrough the use of combustion byproducts of the heating units, but adamaging amount of oxygen is always brought into the oven in the form offresh air makeup.

In either event, the result is that by the time the rubber has beenvulcanized and cured, it has also been subjected to the equivalent of anaccelerated aging process. The result is reduced age resistance, loss inresilience, and tear and crack resistance.

A further diiculty with prior processes has been that the sponge rubberhas had to be specially compounded to not only sag rapidly under theforce of gravity but to then have a blow and cure rate which would matchthe rate of sag.

To obtain these characteristics required a very careful balancing of allthe ingredients in the rubber and often other desirable characteristicsin a sponge rubber padding have had to be sacrificed to obtain thisbalancing.

The present invention contemplates a new and improved sponge rubberpadding which overcomes all of the above referred to difficulties andothers and provides a padding wherein the hollow protrusions have outersurfaces which have been protected from hot gases during the vulcanizingprocess, which are in fact molded, which may be shaped or angled asdesired, and which have an improved surface texture.

The invention also contemplates a product resulting from use of aconveyor belt and method for making such padding which overcomes all ofthe above referred to difticulties and enables the shape, size and depthof the buttons or protrusions to be accurately and consistentlycontrolled lwhile at the same time protecting the surfaces of thevulcanizing or curing rubber from hot oxygen bearing gases.

An important object of the present invention is to provide a new andimproved sponge rubber padding having substantially increased loadbearing characteristics for a given weight of sponge rubber used.

Another object of the present invention is the provision of a spongerubber padding which is economical to manufacture and durable in use.

Still another object of the present invention is the provision of animproved carpet underlay having buttons or protrusions extending fromone side which have a generally iiat bottom surface and substantiallyvertical sidewalls.

Still another object of the invention is the provision o'f a new andimproved carpet underlay manufactured from a blowable sponge rubbercompounded not to balance the sagging, cure and blow rates, but toprovide a firmer, lighter, more resilient and more durable product.

Still another object of the invention is the provision of a new andimproved carpet underlay of blown sponge rubber wherein the rubberduring the vulcanizing and curing process has been exposed to a minimumamount of hot oxygen bearing gases.

Still another object of the invention is the provision of a cushionwhich is the product of a new and improved belt for the manufacture ofsponge rubber underlay which permits the use of tougher, more resilientbase polymers, reinforcing pigments and faster curing systems than willwork fwith the present gravity sag systems of curing.

Still another object of the invention is the provision of a cushionwhich is the product of a new and improved conveyor belt for makingcarpet underlay having a plurality of protrusions or buttons comprisedof a plurality off individual mold members relatively articulated toform such buttons or protrusions to a definite size and shape.

Another object of the invention is the provision of a cushion which isthe product of a new and improved belt for manufacturing carpet underlayhaving a plurality of buttons or protrusions on one surface thereofwhich enables positive pressure control of a relatively high order onthe unvulcanized stock during the curing process.

Another object of the invention is the provision of canpet underlaywherein each individual button or protrusion is molded under a pressuresomewhat greater than atmosphere.

Another object is to provide a belt for a process of manufacturingsponge rubber underlay lwherein curing takes place in an environmentwhich substantially protects it from oxidation damage.

An object also is to provide a cup molded sponge rubber underlaywherein, to improve resistance to compression, iwth the aid of cupsiilled with sponge rubber or molded with thick vertical walls.

Still another object of the invention is to provide a new and improvedsponge rubber cushion, wherein a bridge of molded material is formedbetween adjacent rows of buttons, the bridges acting as a mechanicalinterlock so that the entire area of the cushion is effectively boundtogether, and so that there is provided a larger area of adhesionbetween the backing and the rubber ayer.

In accordance with the present invention, sponge rubber padding isprovided comprised of a plurality of cupped protrusions or buttons of adistinct outer molded shape each having generally vertically extendingsidewalls, a gnerally flat base and integrally joined at the upper eges.

Further in accordance with the invention, each such mold cut has agenerally flat bottom wall and substantially straight and verticalsidewalls and is of a shape allowing arrangement of the mold cups ingenerally contacting side-by-side relationship to form a substantiallycontinuous regularly recessed surface across the entire width and lengthof the belt.

FIG. 1 is a somewhat schematic longitudinal sectional view of apparatuscapable of manufacturing padding according to the present invention;

FIG. 2 is a fragmentary enlarged plan view of a portion of the beltsholwing the hinge arrangement of successive transverse rows of molds;

FIG. 3 is a fragmentary longitudinal sectional view taken along lines3--3 of FIG. 2;

FIG. 4 is a fragmentary cross-sectional view of an end' less belt moldshowing a device for constructing an alternative embodiment of thepresent invention;

FIG. 5 is an illustration representing the progressive separation of thebelt mold from the finished sponge rubber sheet;

FIG. 6 is a fragmentary perspective view of one form of assembled belt;

FIG. 7 is a fragmentary plan view of another lform of assembled belt;

FIG. 8 is a side perspective view of one of the cups of the belt of FIG.7;

FIG. 9 is a fragmentary perspective view of the form of finishedunderlay, made with the belt of FIGS. 7 and 8;

FIG. 9a is a fragmentary sectional view taken on the of hat oxygenbearing gases. line 9a-9a of FIG. 9.

FIG. 10 is a fragmentary plan view of still another form of belt;

FIG. 11 is a side perspective view of one of the cups of the belt ofFIG. 10; r

FIG. 12 is a fragmentary longitudinal sectional view of yet another formof belt;

FIG. 13 is a fragmentary longitudinal view of a composite cushion madefrom the belt of FIG. 12;

FIG. 14 is a fragmentary sectional view of a slightly modified form ofcomposite cushion;

FIG. 15 is a perspective View of one of the cups of the belt used inmaking the cushion of FIG. 14.

Referring now to the drawings of selected embodiments of the inventionchosen for the purpose of illustration, FIG. 1 shows a thin sheet ofuncured, unblown sponge plastic 10, of which natural and syntheticrubber is a typical example compounded with conventional and necessaryblowing and curing agents, being fed from calender rolls 11 onto anauxiliary conveyor belt 12 and then onto an endless main conveyor belt13- constructed in accordance with the invention. This belt '13', asshown, passes over steam heated platens 19 for initial heating of thebelt and then through a source of heat such as an oven 14. A roller ordrum 15 carries the belt 13` at one end and a second drum or roller 16carries the belt at the other end and returns it through a lower section14 of the oven to the drum 15. For picking up the finished product,after it leaves the oven 14, there is a transfer belt 20 which passesthrough a cooling chamber 21 to a location adjacent a wind-up roll 22.

In accordance with the invention, the belt 13 as best shown in FIGS. 2,3, and 6 is comprised of a plurality of individual upwardly opening,cup-like mold members 17 arranged in side-by-side relationship bothtransversely and longitudinally of the belt and so pivoted or hingedrelative to each other in a longitudinal direction that the belt canpass around the rollers or drums at each end of the oven 14. Preferably,these mold members 17 are arranged in a plurality of transverse rows 18,1'8, 18 in side-by-side relationship to form a generally continuousupwardly facing surface on which the sheet of sponge rubber can besupported as it moves through the oven.

Each mold member 17 may take any shape or combination of shapes lendingitself to arrangement in a close adjacent relationship, such as squares,rectangles, hexagons or star shapes, as well as non-geometric shapes,but in the first illustrated embodiment, each mold member in top or planview generally has a diamond shape defined by generally straightvertically extending sidewalls 23, 24, 25, and 26 integral with a fiatbottom wall 27 such that each mold member opens upwardly to define amold cavity of generally diamond shape.

Adjacent rows 1|8v of the mold members 17 may be movably associated soas to pass around therollers 15 and 16 in any desired manner. Preferablythey are hingedly or pivotedly interconnected and in the embodimentshown, the mold members 17 being arranged so that one diagonal isparallel to the length of the belt and the other diagonal extendstransversely thereof and the individual rows 18 overlap in alongitudinal direction with the sidewalls 23, 24, 25 and 26 of one rowparallel to and substantially abutting corresponding sidewalls of theadjacent row. A rod 2'8 extends transversely of the belt throughsuitable transversely aligned openings provided in the sidewalls 23, 24,25 and 26. The openings are preferably located halfway between thetransverse diagonal and the adjacent longitudinal end 29 of each moldmember 17 and are closely adjacent to the liat bottom wall 27 so thatthe belt hinges in its bottom plane. With this arrangement, each row 1.8is pivotally connected to its immediate adjacent.

row. The parallel closely spaced upper edges of the sidewalls 26 form agrid-like surface onto which the sheet 10 of rubber to be cured is fed.

Referring again to FIGS. 2, 3 and 6, pairs of sidewalls 23, 24 and 25,26 forming the longitudinal ends 30' and 31 respectively of each moldmember 17 are so formed to provide a relief 32 between adjacent rows andenable the rows to pivot or hinge relative to each other as they passaround the rollers 15 and 16. Thus the bottom wall 27 at itslongitudinal ends curves upwardly as at 32 and then longitudinally as at34 and then upwardly at a slightly divergent angle as at 35 to the topedge of the respective sidewall. The relief 32 is so locatedlongitudinally that the inner surface of the relief `32 is generallycoaxial and in close contact with the corresponding portion of thesurface of rod 28. This prevents the sponge from blowing between thesesurfaces and locking itself to the belt. The rods 28 are shown as beinground but they can be otherwise shaped as to closely mate with the innersurface of the relief of the mold member. The sidewalls 23, 24, 25 and26 also preferably diverge slightly in an upward direction to provide adraft for facilitating removal of the rubber after it has been molded inthe mold cavity. The bottom wall 27 may have suitable decorativedesigns, not shown, embossed therein. Inner surfaces 39 of the reliefs32 in the bottom wall 27 also provide additional bearing surfaces forthe rods 28.

The size of the individual mold members 17 depends upon a number ofvarious factors such as the plasticity of the blowable rubber sheet andthe ultimate configuration of the lower surface of the carpetunderpadding to be manufactured on the belt. In the preferredembodiment, however, each mold member 17 is approximately of an inch ona side and approximately 1A of an inch deep. Obviously, these dimensionsmay be varied without departing from the invention.

The hinge formed by rod 2-8 extends transversely through all of the moldmembers 17 in one row and the ends thereof may be bent at right anglesor other means may be provided on such ends to prevent theirlongitudinal displacement from the belt.

In the manufacture of carpet underlay in accordance with the presentinvention and using the belt 13 of the invention, it will be appreciatedthat the belt 13 moves continuously through the oven and returns aroundthe rollers and 16, The blowable rubber sheet 10 is calendered to apredetermined thickness by the rolls 11 and is also war-med thereby to asoft and tacky condition.

The sheet 10 supported by the belt 12 moves from the' rolls 11 to thebelt 13 and first comes into supporting contact with the upper edges ofthe members 17 at a supporting portion at 36. Because of its soft andtacky condition, the sheet 10 immediately begins to generatesaggingportions 37 which sag into cavities 42 of the members 17. Thesheet 10 then moves with the belt under a backing sheet 38 which is fedcontinuously to the sheet Il10` from a supply roller 40 at a speedcorresponding to the velocity of the belt 13. The backing sheet 38engages the upper surface of the supported portion 36 and is spaced fromthe sagging portions 37.

The backing sheet is preferably non-porous in the first describedembodiment, and consists of a fabric and a thin sheet of non-blowingrubber calendered thereinto. A feed or pressure roll 41 bears againstthe upper surface of sheet 38 and presses it downwardly to insure fullengagement with all the supporting portions 36. The supporting portionsbeing tacky adhere to the sheet 38. The sagging portions 37 now define aplurality of closed cavities 42. The pressure caused 'by the pressureroll 41 is so controlled that it does not cut through the sheet 10 atthe peripherally supporting portions 36.

The sheet 10, the belt 38 and the belt 13 then move under a preferablyimpervious pressure belt 43, moving at the same speed. This belt 43rests on the upper surface of the sheet 38 and lightly holds it inpressure engagement with the supporting portions 36 while the wholeassembly moves into the heated oven 14.

Within the oven 14, additional means are provided for maintaining thepressure of the belt 43 onto the upper surface of the sheet 38. Suchmeans may take a number of different forms, but preferably such meanstake the form of a drag -belt 44 resting on top of the pressure belt 43arlclv prevented from movement therewith by any suitable means. Thecombination of the two weights insures a seal between the supportingportions 36 and the sheet 38 sufficiently tight to restrict the escapeof gas during the curing operation to produce a differential pressurefrom expanding gases for the molding operation.

As the sheets 10 and 38 continue to move through the oven, they arefurther heated. The rubber in the sheet 10 sags even more into thecavity of the mold members 17, as shown at the right side of FIG. 5. Atthe same time, the rubber of the sheet 10 is heated to a temperaturesuch that the blowing compounds contained therein begin to evolve asgas. This gas causes the rubber to expand. Some of the gas may gettrapped in spaces 46. yOn those occasions when the sheet 38 is animpervious layer the expanding gas backs up against the sheet 38 andforces the sheet 10 downwardly into engagement with the inside metalmold surfaces. Should the sheet 38 be open mesh material, the expandinggas will back up against the pressure belt 43 and the same result willoccur. Then will follow a relatively uniform rapid flow of heat byconduction from the hot metal surfaces of the mold members 17, ascontrasted with the inelfective heating by radiation in former practiceswhere the rubber layer was merely suspended on a wire mesh. In theformer practice the limited heating by conduction where the ru-bbersheet folded over the wire actually created a detrimental unevenheating, much slower than the present technique.

The pressure created, as described, is sufcient to slightly densify theexternal surface on the rubber in engagement with the surfaces of themold members 17 and to, in effect, give to the rubber a relatively toughimpervious skin. Also, and more importantly, the rubber, instead ofexpanding outwardly simply against atmospheric pressure, takes on acharacteristic similar to that when expanded into a mold. Trapped air inthe cavities 42 when treated in the oven assists in pressing thematerial of the sheet 10 into the mold member 17, as the trapped airexpands when heated.

Tests have shown that the same compound cured on a conventional openwoven wire belt is considerably inferior in compression deflectioncharacteristics than the compound molded while it is being cured asabove described.

The curing compounds contained in the rubber of sheets 10 and 38 nowbegin to take effect and the blown and shaped material of sheet 1 0 andthe rubber of sheet 38 cure in the shape shown at the left end of FIG. 5with sheet 38 rmly adhered to the supporting portions 36.

After the curing and blowing operation just described is completed, thebelt 13 moves the sheets 10 and 38, now indicated as composite cushion45, from beneath the pressure belt 43 and thereafter the compositecushion 45 is removed from the belt 13, picked up by the transfer belt20 by which it is passed through the cooling chamber 21 and from thereto the wind-up roll 21 where it is wound into rolls 46 for shipment.

The belt 13 meanwhile passes downwardly around the roller 16 and movesback to the entrance end of the oven 14, where it again passes aroundroller 15 and returns to the position to accept the uncured rubber sheet10 from auxiliary conveyor belt 12.

It will be appreciated that in some instances the backing sheet 38 maybe omitted, assuming that its lateral strength is not needed or the'backing sheet 38 need not go through the oven with the sheet 10 butinstead may be cemented to the blown sponge cup molded rubber after therubber has completely cured and even cooled. Also a simple fabricwithout any rubber filling its interstices may be employed. In any ofsuch events, the pressure belt 43 should then be gas impervious so thatthe gases released by the blowing rubber are still trapped withincavities formed by the sagging rubber portions 37 and the lower surfaceof the Vbelt 43. The belt 43 should preferably be made of a gasimpervious material. A typical satisfactory material is Silicon orTeflon coated glass fibre.

While many portions of the apparatus are to a degree conventional, thebelt 13 used with the apparatus is one peculiarly adapted to thepractice of the invention. The sponge rubber composite cushion, made inaccordance with the invention, may have, when viewed from the bottomside, a plurality of discrete generally diamond shaped buttons orprojections 50 of blown, cured rubber having an outer surfacecorresponding to the shape of the inside of the mold members 17 anddefined by the generally flat bottom wall 27 and generally straightvertically extending sidewalls 23, 24, 25 and 26. The sidewalls ofadjacent 'buttons 50 are generally parallel and spaced a distance apartequal to the thickness of the abutting sidewalls of the mold members 17.The outer surfaces of the buttons 50 have a distinct appearance ofhaving been molded and as such have what may be referred to as areinforcing skin. All buttons are of exactly the same vertical height.Should members 17 of varying heights be employed, the buttons would havea similar variation in height. The flat bottom wall 27 is interruptedacross one corner by a depression or groove resulting from the rods 28which pass on the inside of the mold member 17.

The buttons 50 are integrally joined by a thin web 51 at the upper endsof the sidewalls. This web generally has been prevented from blowing bythe weight of the belt 43 and is of somewhat denser rubber. In thecomposite cushion of the preferred embodiment, the sheet 38 is adheredto the upper surface of this web 5-1 so that viewed from the top, thecomposite cushion of the preferred embodiment has a continuous flatsurface, but the cushion itself has a plurality of sealed cavitiesimmediately under this sheet 38 and otherwise defined by the buttons 50.Absent the sheet 38, the sponge rubber itself underneath is made up of aseries of upwardly facing concavities.

In the embodiment of the invention illustrated in FIGS. 7, 8 and 9alterations are made in the construction of cup-like mold members 55,one of which is pictured by itself in FIG. 8. Each mold member consistsof sidewalls 56, 57, 58 and 519. Sidewalls 56 and 57 converge to form acorner 60 and sidewalls 58 and 59 converge to form a corner 61.Similarly sidewalls 56 and l59 converge to form a corner `62 whereassidewalls 57 and 58 converge to form a corner 63. Axially alligned holes64 and 65 are provided in the sidewalls 56 and 57 respectively toaccommodate one of the rods 66. Similar holes 67 and 68 are providedrespectively in the side walls 58 and 59, likewise to accommodate one ofthe rods 66.

The sidewalls 56, 57, 58 and 59 together with a bottom wall 69 form acavity indicated generally by the reference character 70. Below thecorners 60 and 61 respectively are reliefs 72 and 73, formed by bendingadjacent the corners of the bottom wall `69 upwardly whereby to provideadditional support for the respective rods 66 when they are threadedthrough the holes provided for them. Also the sharp inside corners atthese points are somewhat diflicult to fill with expanding sponge rubberand by providing. the reliefs a neater over-all finish is produced.

Of special importance is the provision of cutouts in the sidewalls andtypical of these is the cutout 74 which extends inwardly from an edge 75of the sidewall 56. Similarly cutouts 76, 77, and 78 are formed in thesidewalls 57, 58 and 59 respectively. In addition there are providedcutouts 79 and 80 at opposite ends of the sidewall 56. A matching cutout81 in the sidewall 57 adjoins the cutout 79 and a matching cutout 82 inthe sidewall 59 lies opposite the cutout 80. The other corners 61 and 63are provided with similar cutout portions. Extending upwardly orinwardly of the bottom wall 69 is a protuberance 8'1 which extends intothe cavity 77`.

All of the mold members l55 are identical and are hinged together byemployment of the rods 66 in the manner illustrated in FIG. 7 to form aconveyor belt indicated generally by the reference character 82. Theconveyor belt 82 is made up in substantially the same fashion as themain conveyor belt 13 heretofore described.

The operation for making use of the conveyor belt 82 is the same as theoperation described in connection with FIGS. l through 5 inclusive,wherein a sheet of blowable sponge rubber is applied first to the edgesof the sidewalls like the edge 75, over which is applied a backing sheetlike the backing sheet 38. The two sheets are then passed through theoven 14, this time in position upon the conveyor belt 82 wherein thesame expanding of the blowable sponge rubber sheet takes place. Theproduct resulting from use of the conveyor belt 82 is the compositecushion y83 shown in perspective in FIG. 9. On this occasion, however,deformation of the sheet 10 results in the formation of buttons 84 ofslightly different configuration. The cutouts 74, 76, 77 and 78 resultin the formation of bridges 85 which span recesses 86 and 87 therebyinterconnecting every side of all of the buttons 84. In addition bridgefillers 88 are formed at each four corner intersection as a result ofblowable sponge rubber from the sheet l10 filling the cutout spaces suchas those formed by the cutouts 79, 80, 79 and 80. A sheet 38 is fastenedto the edges 75 of the buttons 84 in the same manner as heretoforedescribed.

Further still, by providing protuberances 81 on only certain of the moldmembers 55, such for example as those selected and depicted in FIG. 7.The protuberances can be arranged in the form of letters or figures,such for example as the letter A of FIG. 7. When this is done, theprotuberances will form complementary depressions at midportions of theresulting tops of the buttons 84 and these depressions can be used tospell out letters, numbers and signs.

lWhen a composite cushion like the cushion I83 is formed in the mannerdescribed, there will be considerably more resistance to folding andbending of the composite cushion once it has been formed and cured.

Still other pattern effects can be produced by building sundryconfigurations into the walls of cup-like mold members, like for examplethe mold members 90 of FIGS. 10 and ll. One such mold member is shown inperspective View in FIG. ll and a multiplicity of such mold members areshown in FIG. 10 made into a conveyor belt indicated generally by thereference character 9.1 wherein they are hingedly linked by rods 92.

As shown in FIG. ll the mold members 90 have sidewalls 93 and 94. Thesidewalls 93, for example, has a semi-cylindrical exteriorly convexportion 95, provided midway between opposite endswith a cutout 96.Additional cutouts 97 and 98 at respective opposite ends join respectivefillets 99 and 100. IFlat portions 101 and 102 lie below the respectivecutouts 97 and 98. Holes l103 and 104 are provided in the at portions.101, and 102, the holes being for the accommodation of rods 92.

The sidewall 94 is similarly formed with an exteriorly convexsemi-cylindrical portion 105, fillets 106 and 107, and interconnectingfiat portions 108 and |109. A cutout 110 is provided in the convexportion 105 and cutouts 11-1 and 112 on opposite sides of it. By makingall of the mold members 90 identical, they iit together in the uniquepattern illustrated in FIG. l0 and when the conveyor belt 91 of FIG. 10is used to load a composite cushion similar to the composite cushions 45and 83, a new composite cushion will result. The cushion 91, however,will have the characteristic pattern initially built into the conveyorbelt 91. Because of the cutouts described in FIG. 1l, as well as thefillets, the cushion 91 will enjoy the advantages of the interconnectingbridge fillets described in connection with FIGS. 7, 8 and 9'.

IWhen a substantially at composite cushion like the composite cushion'115 of FIG. 13 is desired, shallower cup-like mold members `116 aremade use of. In this instance mold members will have sidewalls 117, 118,119 and 120 and a bottom wall 121. 'If desired, these can be made up ina diamond-like form such as illustrated in FIGS. 2 and 7, for example,or in some other form such as is exemplified by FIG. ll. Moreparticularly in this form, however, the sidewalls are only slightlygreater in height than the diameter of rods 122. When the mold members116 are hinged together by rods 122, they form a conveyor belt indicatedgenerally by the reference character 123, and this belt used in the samemanner as described in connection with FIGS. l through 5 inclusive. Theresulting product will be a product like the composite cushion 11S inwhich an upper side 124 will be substantially flat as is also a lowerside 125. Relatively narrow air spaces 126 remain in the interior. Oneof the advantages is that the cushion with opposite flat surfaces meetscertain critical specification where a greater degree of compressiveresistance is desired.

If desired, the sheet may be compounded so that when heated to createsponge rubber, the sponge rubber completely fills the mold member 17leaving on depression of the nature of those heretofore described aspresent in the composite cushion 83. A cushion of this description hasgreatly enhanced compression resistance and all the benefits of thebridges described and shown in FIGS. 9 and 9a.

Another form of the product providing relatively greater resistance tocompression is shown in FIG. 14 and is formed by use of cups like thoseshown in FIG. 15 made up into an appropriate belt. The deep indentationsare formed in mold members 127 by appreciably enlarged protuberances128, similar in function to the protuberances 81. A decorative characterlike the triangle 129 may be added to the protuberance 128. The enlargedprotuberance 128 provides a deep depression 130 in molded elements 131carried by what may be an open mesh sheet 132 of a composite cushion133. Relatively thick sidewalls 134, in this form of cushion, have alarge expanse of vertical surface, and act as strong weight supportingcolumns, stiffened by bridges 85 and 88. There is also appreciablygreater metal to rubber surface contact in a mold member suited to formthe molded element 131 and therefore a more rapid uniform transfer ofheat from the hot belt to the rubber results. Oven time for producingthe composite cushion 133 is therefore shorter.

It will thus be seen that embodiments of the invention have beendescribed which accomplish all of the objects of the inventionheretofore set forth and others and that a carpet underlay and a beltand method of manufacturing same have been described which are novel andproduce highly improved results.

In particular, such results may be generally defined as a carpetunderlay having a plurality of buttons all of a uniform verticalthickness, all having a generally at bottom surface, all havinggenerally vertical sidewalls, and al1 having the lower exposed surfaceswith a molded texture and contour which are pleasing in appearance.

The rubber employed, instead of being compounded as a balancing ofsagging, blowing and curving characteristics, can be compounded to givemaximum resilience and maximum life. It will be apparent that the rubberitself during the course of curing has been exposed a minimum amount tohot oxygen bearing gases and therefore should have a maximum life andhighly improved other characteristics.

Having described the invention herein, what is claimed as new and soughtto be secured by Letters Patent is:

1. A composite cushion of relatively resilient material comprising twosheets of diierent composition, form and thickness, one of said sheetscomprising a substantially flat sheet of impervious stretch resistantnon-blown rubber material providing a continuously uninterrupted area onone side, a second sheet of blown sponge rubber material comprising amultiplicity of buttons on the side facing away from said flat sheet, aseries of long narrow recesses in mutually intersecting relationshipseparating sides of said buttons one from another, and bridges ofmaterial of said second sheet spanning said recesses and integrallyjoined to the sides of said buttons and said flat sheet, whereby toprovide an interconnecting system of bridging sections for the buttonsthroughout the area of said composite cushion.

2. A composite cushion of relatively resilient material comprising twosheets of different composition, form and thickness, one of said sheetscomprising a substantially flat sheet of impervious stretch resistantnon-blown rubber material providing a continuously uninterrupted area onone side, a second sheet of blown sponge rubber material comprising amultiplicity of buttons on the side of said sheet facing away from saidat sheet, said buttons having central cavities therein, edges of saidcavities being in adhesive engagement with edges of adjacent cavitiesand adjacent areas of said substantially at sheet, a series of longnarrow recesses in mutually intersecting relationship separating sidesof said buttons one from another, bridges of material of said secondsheet extending into and spanning inner portions of said recessesadjacent said edges and integrally joined to the sides of said buttons,whereby to provide an interconnecting system of bridges for the buttonsthroughout the area of said composite cushion.

3. A cushion according to claim 2, wherein a central portion at thebottom of each depression extends inwardly whereby to provide arelatively thick perimetral sidewall.

4. A composite cushion of relatively resilient material comprising twosheets of different composition, form and thickness, one of said sheetscomprising a substantially flat sheet of impervious, stretch resistancenon-blown rubber and fiber reinforcing material providing a continuouslyuninterrupted area on one side, a second sheet of blown sponge rubbermaterial comprising a multiplicity of buttons on the side facing awayfrom said flat sheet, a series of long narrow recesses in mutuallyintersecting relationship separating sides of said buttons one fromanother, bridges of material of said second sheet spanning said recessesand integrally joined to the sides of said buttons, and bridge illers ofmaterial of said second sheet joining all mutually adjacent corners ofsaid buttons, whereby to provide an interconnecting system of bridgesand bridge llers for the buttons throughout the area of said compositecushion.

S. A composite cushion as in claim 1 wherein said Hat sheet is a liberreinforced non-blown rubber sheet.

6. A composite cushion as in claim 1 wherein said long narrow recesseshave a width no greater than the thickness of walls forming saidbuttons.

7. A composite cushion as in claim 1 wherein walls forming said buttonsare substantially perpendicular to the plane of said at sheet.

8. A composite cushion as in claim 1 wherein bottoms of said buttons areflat and lie in a plane parallel to the plane of said at sheet.

References Cited UNITED STATES PATENTS 2,739,093 3/1956 Bull 161-1272,821,244 1/1958 Beck 161-127 3,231,454 l/l966 Williams 161-1223,285,793 1l/1966 Chavannes 161-122 3,294,387 12/1966 Chavannes 161-127MORRIS SUSSMAN, Primary Examiner

